The goalkeeper captain Buffon, 38, and the 35-year-old defender Barzagli have helped Juve win their last five successive league titles.
Both were in the Italian national squad that won the 2006 World Cup, Barzagli then being a reserve, and are set to man the Azzurri’s defence at Euro 2016 in France.
Barzagli has been at Juve since 2011 after transferring in mid-season from German club Wolfsburg, where he won the Bundesliga in 2009. He had earlier stints in the Serie A at Chievo and Palermo.
Buffon has won seven titles with Juve since his arrival from Parma in 2001.
Juventus coach Massimiliano Allegri also renewed his contract until 2018 last week.